RU2318855C2 - Clayless drilling mud - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: invention relates to drilling oil and gas wells, namely to clayless biopolymer drilling muds used to expose productive formations of horizontal wells and inclined wells deviating from vertical by more than 1000 m, represented by carbonate and terrigenous reservoirs, as well as to restore wells by drilling second wellbores under different geologic conditions. Drilling mud contains, wt %: biopolymer (ASG-1 or Ritizan-M) 0.3-0.8, modified starch 1.0-2.5, organic inhibitory additive (FK-2000 Plus M) 8-12, potassium chloride 1.5-3.0, marble crumb 1.5-3.0, and water - the rest.

EFFECT: reduced drilling mod filtration and enhanced surface-active properties with regard to formation fluid.

1 tbl, 4 ex

Description

The invention relates to the drilling of oil and gas wells, namely, clayless biopolymer drilling fluids used to open productive formations of horizontal wells and directional wells with a vertical distance of more than 1000 m, represented by carbonate and terrigenous reservoirs, as well as to restore wells by drilling the second trunks in various geological conditions.

Drilling fluids for drilling horizontal and directional wells with a vertical distance of more than 1000 m should have the following characteristics:

- stable structural and rheological properties to provide the necessary carrying and holding ability, preventing the formation of the Baikot effect;

- low rate of filtration of the drilling fluid into the reservoir, which helps to reduce the skin factor during the initial opening;

- high inhibitory properties of clay components of the reservoir;

- high surface-active properties, namely: low values of interfacial tension at the boundary of the mud filtrate - hydrocarbon; values of the contact angle should be more than 100 °;

- lubricating properties to improve the working conditions of the rock cutting tool at the bottom, facilitate the passage of the drill string and prevent sticking;

- resistance to polymineral aggression.

The main volume of drilling horizontal and directional wells with a large deviation from the vertical is carried out with drilling fluids based on biopolymers.

Known clay-free drilling fluid containing a biopolymer, inorganic salt and water [RF patent 1774946, class. C09K 7/02, 1990]. The known solution has high rheological and structural-mechanical properties, a low coefficient of pseudoplasticity "n", which provides the solution with the necessary carrying and holding abilities when drilling a horizontal section of the well.

At the same time, this solution has low lubricating properties. In addition, with high rheological and structural-mechanical properties, the known drilling fluid is characterized by an extremely high consistency index “K” and, therefore, large hydraulic resistances.

Hydrocarbon-based drilling fluids have high lubricating and surface-active properties, have maximum affinity for the formation fluid, but insufficient holding and carrying capacity. The presence of hydrocarbon components in the solution distorts the readings of gas logging, which limits the use of the solution when drilling wells in difficult geological conditions, which are characterized by the proximity to the reservoir of gas and aquifers.

A known solution based on a water-oil emulsion, including clay, caustic soda, carboxymethyl cellulose, multifunctional surfactants, polymer and water [RU 2231534, cl. C09K 7/02]. Known solution has a low filtration rate, good lubricating properties, but insufficient durability. The presence of a solid phase in the solution negatively affects the performance of the bits.

Closest to the claimed technical solution is a non-clay water-based mud containing biopolymer, potassium chloride, modified starch, calcium carbonate and water [see US patent No. 4098700 from 04.07.78].

The disadvantage of this solution is the use of imported biopolymer in its composition, which increases the cost of the solution, insufficiently high inhibitory ability, low surface-active and tribological properties.

The technical problem solved by the present invention is to obtain an inhibitory non-clay pseudoplastic drilling fluid based on water with low filtration rates into the formation and high surface-active properties with respect to the formation fluid, ensuring the quality of the initial opening at the level of skin factor not exceeding +1.

The specified technical problem is solved in that the inventive clayless drilling fluid containing biopolymer, potassium chloride, modified starch, calcium carbonate and water, as a biopolymer contains a chemical reagent ASG-1 or Ritizan-M, as calcium carbonate - marble chips and additionally contains FC-2000 Plus M organic inhibitory additive in the following ratio of ingredients, wt.%:

biopolymer 0.3-0.8 potassium chloride 1,5-3 modified starch 1.0-2.5 marble chips 1,5-3 organic inhibitor supplement FC-2000 Plus M 8-12 water rest

The presence of a biopolymer in the drilling fluid in combination with other ingredients provides low filtration rates (V _f -10 ^-7 m / s) due to the pseudoplastic and thixotropic properties of the mud filtrate, which are associated with both the destruction of the structure of the entire system and the accumulation of highly elastic deformations. These deformations and fractures undergo a spatial supergrid, the nodes of which are formed by overlaps of single chains of biopolymer macromolecules. The high inhibitory properties of the proposed biopolymer drilling mud are enhanced in the joint presence of potassium chloride and, for example, FC-2000 Plus M, which indicates a different mechanism of inhibition of clay components. If the potassium cation (K ⁺ ) mainly affects osmotic processes and capillary impregnation by blocking the interlayer channels of the crystal lattice of clay minerals, the inhibitory component of FC-2000 Plus M, which is a lubricating additive, exhibits additional inhibitory properties in the claimed composition due to adsorption and chemisorption effects reduces diffusion processes of surface hydration, and the additional introduction of a filtration reducer prevents the penetration of the filtrate into the rock.

To ensure the affinity of the drilling fluid filtrate with the formation fluid and to reduce the interfacial tension at the boundary “drilling fluid filtrate - hydrocarbon” (which is especially important for the initial opening of the reservoir), we used the complex organic inhibitory additive FK-2000 Plus based on triglyceride fatty acids, which salts of fatty acids are also included.

To prepare the inventive drilling fluid, the following materials and chemicals were used:

1. Biopolymer ASG-1, TU 2231-001-49472578-01.

2. Ritazan-M, TU 9291-002-58114197-2004.

3. Modified starch, TU 2262-016-32957739-01.

4. Organic inhibitor of FC-2000 Plus M, TU 2458-002-49472578-03.

5. Potassium chloride, TU 2152-013-00203944-95.

6. Marble chips, TU 5716-006-49119346-01.

7. Technical water.

The essence of the invention is illustrated by the following examples.

Example 1. To obtain the claimed drilling fluid, 8 g of industrial water was added 3 g of ASG-1 biopolymer, 10 g of modified starch, mixed until the reagents were completely dissolved, then 15 g of potassium chloride, 15 g of marble chips with an average median particle diameter of 45 to 100 microns, stirred for 0.5 h and 80 g of FC-2000 Plus M inhibitory additive was added. After 0.5 h of stirring, a composition was obtained with the following ratio of components, wt.%: ASH-1 0.3%, modified starch 1%, potassium chloride 1.5%, marble chips 1.5%, inhibi FK-2000 Plus M additive 8%, water the rest.

Example 2. To obtain the claimed drilling fluid, 7 g of ASG-1 biopolymer, 25 g of modified starch were added to 788 g of industrial water, mixed until the reagents were completely dissolved, then 30 g of potassium chloride, 30 g of marble chips with an average median particle diameter of 45 were added up to 100 microns, was stirred for 0.5 h and 120 g of FC-2000 Plus M inhibitory additive was added. After 0.5 h of stirring, a composition was obtained with the following ratio of components, wt.%: ASH-1 0.8%, modified starch 2.5%, potassium chloride 3%, marble chips 3%, inhibi uyuschaya additive FC-2000 Plus M 12% water the rest.

Example 3. The drilling fluid was prepared analogously to example 1, but instead of the biopolymer ASG-1 took Ritizan-M.

Example 4. A drilling fluid was prepared analogously to example 2, but instead of the biopolymer ASG-1, Ritizan-M was taken.

The properties of the resulting drilling fluids were analyzed in laboratory conditions.

The surface tension (σ, mN / m) of the mud filtrate was measured on a stalagmometer of the Ufa Research Institute for drop separation at the filtrate-hydrocarbon interface.

Tribological (lubricant) mud properties measured on the apparatus from «Baroid» friction coefficient couples metal-metal at a load of 150 lb / ^in2.

The inhibitory ability, which is characterized by indicators of moisturizing ability (P ₀ ), was determined on samples of pressed sarigukh bentonite with a diameter of 20 mm and a height of 32 mm according to RD 39-00147001-773-2004.

Structural and rheological characteristics: plastic viscosity (η _PL , mPa · s), dynamic shear stress (τ ₀ , dPa), gel strength (Gels _{10 '' / 10 '} , dPa) were measured on a Fann 35SA viscometer, pseudoplasticity index “n” and the consistency index “K” was calculated according to known standard formulas.

The filtration rate (F ₃₀ , cm ³ ) was measured on a Fann filter press at a temperature of 20 ° C and 90 °.

The table shows data on indicators of the properties of the proposed solution at the minimum and maximum ratio of ingredients.

Structural and rheological properties Example 1 Example 2 Example 3 Example 4 Conditional viscosity, _700/500 s 34 45 28 40 Density, kg / m ³ 1020 1050 1020 1050 Plastic viscosity, MPa · s 12 16 17 17 Viscosity at low shear rates (VNSS), MPa · s 1100 1500 1000 1300 Static shear stress 10`` / 10 ', dPa 35/45 60/70 30/40 50/65 Dynamic shear stress, dPa 138 194 158 184 Nonlinearity 0.39 0.39 0.44 0.4 The consistency coefficient, Pa · s ⁿ 1.75 2.47 1,58 2.23 Filtration properties The filtration rate at 20 ° C, cm ³ four 2,5 four 3 The filtration rate at 90 ° C, cm ³ 6 four 7 5 The rate of filtration in the reservoir, V _f , 10 ^-7 m / h 5 four 5.5 four Tribological properties Coefficient of friction 0.12 0.10 0.12 0.10 Inhibitory and surface active properties Coefficient of surface tension, mN / m 5 3 6 3 Wetting angle, deg 113 128 111 131 Moisturizing ability, P ₀ , cm / h 1.6 · 10 ^-3 1.2 · 10 ^-3 1.56 · 10 ^-3 1.28 · 10 ^-3

The data shown in the table show that the inventive solution has low values of the filtration rate, technologically necessary for drilling horizontal and directional wells with a large angle of deviation from the vertical wells structural and rheological characteristics of the solution, providing a degree of cleaning of the barrel of more than 85%, improved lubricating properties to avoid puffs and sticking of the tool, high inhibitory properties that prevent hydration and swelling of clay components of the collector, filtrate the drilling fluid has low surface tension at the border with the hydrocarbon fluid, low filtration rates provide minimal negative impact on the reservoir.

The inventive solution was used when drilling more than 30 wells in the fields of OAO Slavneft-Megionneftegaz. All wells went into production without delay with expected flow rates.

Claims (1)

A clay-free drilling fluid containing a biopolymer, potassium chloride, modified starch, calcium carbonate and water, characterized in that it contains ASG-1 or Ritizan-M as a biopolymer, marble chips as calcium carbonate and additionally contains an organic FC inhibitory additive -2000 Plus M in the following ratio of ingredients, wt.%: biopolymer 0.3-0.8 potassium chloride 1.5-3.0 modified starch 1.0-2.5 marble chips 1.5-3.0 organic inhibitory supplement FC-2000 Plus M 8-12 water rest